DE102005009786A1 - heater - Google Patents

Abstract

The invention relates to a heater (10), in particular a motor vehicle heating device (10), which has means for determining a temperature and / or acting as overheating protection means. DOLLAR A According to the invention it is provided that the means for determining the temperature and / or acting as overheating protection means comprise a working according to the calorimetric measuring principle flow sensor (12). DOLLAR A Furthermore, the invention relates to the use of a known, working according to the calorimetric measuring principle flow sensor (12) as a temperature sensor and a method for determining a temperature and / or to provide an overheating protection.

Description

The The present invention relates to a heater, in particular a motor vehicle heating device, comprising means for determining a temperature and / or as overheating protection working Having means. Furthermore, the invention relates to a new use for one according to the calorimetric measuring principle working flow sensor.

For example in motor vehicle heaters, which serve as additional and / or auxiliary heating, the system security by overheating protection be ensured. This is especially true when it comes to a heater in which a liquid Heat transfer medium is heated, at the desired Place heat to be able to deliver. About that out is the knowledge of the current temperature of the heat transfer medium for the Control or regulation of the heater important.

At the The state of the art has been used for overheating protection and temperature measurement generally uses at least two sensors. For example, it is known that overheating protection by a PTC to realize a bimetallic switch or a fuse link. For temperature determination is usually a temperature-dependent resistance (NTC) used.

Furthermore it is known the evaluation of temperature gradients as additional Safety criteria. It is assumed that an unusual one strong temperature rise resulting from a device or system fault.

Of the Use of the above known temperature sensors as overheating protection or for temperature measurement, however, associated with some disadvantages. For example, the reliability Although it is very high in bimetallic switches, it is not software-based Diagnosis of the condition of the supply lines regarding function, short circuit or Interruption possible. Including the required supply lines, fasteners, Connector, etc., the bimetal switch is a relatively expensive component. Furthermore, the contact of the bimetallic switch with the heat transfer medium a big Influence on the function. This one for the correct functioning The bimetallic switch can provide important thermal contact in many Cases about the Service life of the heater not sure assured because of problems with mounting safety, corrosion and deposits occur in the heat exchanger can.

A Reaction to a dangerous Condition takes place in the known solutions only after reaching the component-specific switching temperature. This also applies to the use a PTC or a fuse as overheating protection. A fusion insert has moreover the disadvantage that it is destroyed by a trip and replaced got to.

The Evaluation of temperature gradients has the disadvantage that this Principle especially in the so-called dry overheating fails, for example then occurs when there is no or too little cooling water in the system. Such a failure is due to the fact that in this case existing cooling medium (For example, air or water vapor) due to the lower heat capacity and the lower thermal conductivity causes that the temperature sensor overheats delayed detected, causing damage to the heater to lead can.

Of the Invention is based on the object, the generic heaters so to further develop that avoids the problems explained above and at the same time the possible uses of known, according to the calorimetric measuring principle working flow sensors, be enlarged.

These The object is solved by the features of the independent claims.

advantageous embodiments and further developments of the invention will become apparent from the dependent claims.

The heater according to the invention builds on the generic state of the art in that the means for determining the temperature and / or acting as overheating protection means comprise a working according to the calorimetric measuring principle flow sensor. This solution is based on the finding that a commonly used as a calorimetric flow sensor element can be used as a temperature sensor, both as a temperature sensor for overheating protection and as a temperature sensor for temperature measurement. It is particularly possible to use only a single element for the realization of temperature detection and overheating protection. This element preferably has a maximum of four and ideally two contacts, which will be explained in more detail later. The entire cost of the previously used as overheating protection device can be omitted. Since it is used in accordance with the invention used according to the calorimetric measuring flow sensor it is possible to evaluate an energy removal instead of a limit temperature, critical states can be detected long before reaching a limit temperature. This considerably improves the reaction speed of the system and considerably increases safety. In particular, the above-mentioned problem of dry overheating is reliably controlled by the solution according to the invention, since the Strö tion sensor detects the low energy removal long before reaching a critical temperature. This allows the heater to withstand multiple dry overheating without damage.

at the preferred embodiment the heater of the invention is provided that the flow sensor is arranged so that it at least partially from a heat transfer medium is surrounded. In connection with a motor vehicle heating device, the Heat transfer medium especially by cooling water be formed, which is heated by the heater to the recorded Heat later, at least partly at the desired Place again. In this case, the flow sensor is preferably in Area of the heat exchanger of the heater intended. However, in the heater according to the invention, it can also around an air heater act in which the warming a room provided air is heated directly. In this case is the flow sensor preferably arranged in a stream of air. Alternatively, the flow sensor be housed in a solid medium, since the inventive use a flow sensor everywhere works where a flow of energy takes place.

Farther it is preferred that the flow sensor a heating element and a temperature measuring device. When Heating element comes in particular a heating resistor and as Temperature measuring device, a temperature-dependent measuring resistor into consideration. The heating resistor and the measuring resistor can be separated via two Cables are controlled so that the sensor element in this case has four contacts. Alternatively, it is possible to use the heating resistor and To couple the measuring resistor so that a center tap provided is, in which case the sensor has three contacts.

at the most preferred embodiment However, the heater of the invention is provided that the heating element and the temperature measuring device are formed by a component or a component group, the or alternately as a heating element and as a temperature measuring device is operated. For example, a suitable resistance element alternating as heating resistor and as temperature-dependent measuring resistor be used so that the sensor have only two contacts must, which makes the sensor very reasonably priced. Even if the solution With only one element is particularly economical, it can at Systems, for the one increased Safety is required, be useful, in addition to the preferred taking place short-circuit verification, Interruption, function and plausibility at least one more redundant System use. In this case, so is an embodiment with two resistive elements acting as heating and temperature measuring device serve, meaningful. It is assumed that both resistors have temperature dependencies have, whose characteristics are known. So it is in a steady State possible, by measuring the resistance value at the one resistor close the ambient temperature, and from this ambient temperature to determine what resistance value the second resistor should have. Lies the deviation of this setpoint from the actual value except half a tolerable range, there is an error in the sensor, the software side to initiate appropriate measures to lead should. Such a measure For example, may be a Störverriegelung be the vehicle heater. It is advantageous if the nominal values and If necessary, differentiate the characteristics of both resistors, so that Property changes, that is called especially parasitic resistances, drifting and material changes, have different effects on the measurements relative to the norm curves. The review can cyclically and as often as between the normal working cycles of the sensor, so also during the burning operation of the vehicle heating, be repeated.

It is preferred that a defined energy supply can take place via the heating element and that an energy removal can be concluded via a subsequent cooling detected by the temperature measuring device. It is assumed that the energy-transporting cooling medium must be able to carry away at least the same amount of energy as is introduced by the heating. It is completely irrelevant with what speed the heat transfer medium flows or how high its heat capacity. The only thing that is important is the determined course of the cooling curve, which is a measure of the energy balance of the system and, in addition, depending on the length of the cooling phase, the media temperature directly measure or can conclude by extrapolation. The essential difference from the gradient evaluation mentioned in the introduction is that according to the invention a defined electrical heating of the sensor is provided, which represents a defined energy supply and, as a result, can be deduced by the subsequent cooling to a defined energy removal. A critical energy balance (to ge energy removal) is an essential criterion for protecting the system from overheating and can be detected well before it reaches a critical temperature and can be used as a threshold to initiate safety measures. It is particularly advantageous for the reaction speed of the sensor when the thermal inertia of the sensor is low.

One Another aspect of the present invention relates to the use a working according to the calorimetric measuring principle flow sensor as a temperature sensor. Such flow sensors are based on that over the ambient temperature heated sensor element of the energy is withdrawn from the surrounding medium. The sensor element is cooled, and all the more so, the stronger the medium flows or the higher its thermal conductivity and its specific heat capacity. The cooling or heating curves of the sensor usually follow an asymptotic e-function. The use of such flow sensor as a temperature sensor is among other things particularly advantageous because at any time a diagnosis of the supply lines Short circuit or interruption exists. The correct function of the Component can be checked at regular intervals, by heating the element and before and after the resistance is measured. For an intact sensor element becomes a change in the resistance value provided. Changes the resistance is not, it must be assumed that a defect. Unlike the conventional one Use of calorimetric measuring principle flow sensors are in the use according to the invention no knowledge of the media properties required because preferably detected only on a sufficient energy removal becomes.

All over, where cooling and / or heating play a role in balancing energy balance System requirement for the protection against critical conditions, and everywhere There, the use of the invention a working according to the calorimetric measuring principle flow sensor as a temperature sensor, i. as overheating protection and / or as a sensor for determining the temperature, are used. The application is not limited to liquid media. This Principle works everywhere where an energy flow takes place, including in gaseous and solid media. This does not even require a movement of the medium (For example, when the thermal conductivity is good enough to excess energy carry away). As a major innovation in sensor technology is considered the heating of the measuring element, the from the sensor a system with its own evaluable energy balance makes. Of the Sensor and the one to be protected System are suitable to match.

When It is considered particularly advantageous that the flow sensor the function of overheating protection Has. In conventional as overheating protection used temperature sensors performs an example by Calcification and / or deposit formation on the top or contact surface caused Deterioration of the thermal conductivity to a shift of the switching threshold in the direction of higher temperatures, so that the system is more heavily loaded becomes. In contrast, leads a deterioration due to aging thermal conductivity and thus the energy removal in the inventive use of a flow sensor as overheating protection to make the gradients flatter, that is, one Reaction point shift leads to shift the switching threshold in the direction of lower temperatures, so that critical states earlier be recognized.

Farther can be provided according to the invention be that the flow sensor intended to determine the temperature. It is called as particularly advantageous if a single flow sensor both as overheating protection as well as for temperature measurement is used, since in this case instead of the usual for this purpose used two components only one component is required. The temperature can be measured directly or determined by extrapolation become.

For the use according to the invention it is preferred that the flow sensor a heating element and a temperature measuring device. In This connection is used to avoid repetition of the corresponding versions referenced in connection with the heater according to the invention.

The same applies mutatis mutandis to the case that is provided that the heating element and the temperature measuring device are formed by a component or a group of components, the or the operated alternately as a heating element and as a temperature measuring device becomes.

Farther is also preferred in connection with the use according to the invention that on the Heating element takes a defined power supply and over a detected by the temperature measuring device, subsequent cooling an energy transfer is closed. Also in this regard is to the explanations referenced in connection with the heater according to the invention.

The The invention further relates to a method for determining a temperature and / or for providing overheat protection in a vehicle heater, in which using a calorimetric measuring principle working flow sensor at least two times a temperature of a heat transfer medium is measured.

• – T die Temperatur und t die Zeit bezeichnet;
• – a den Abstand des Anfangspunktes von der Asymptote (a+c), das heißt die Ausgangstemperatur darstellt;
• – b ein Maß für die Kombination der Stoffeigenschaften Wärmeleitfähigkeit und spezifische Wärmekapazität und die Strömungsgeschwindigkeit des Wärmeträgermediums ist, beziehungsweise ein Maß für den Energieabtransport; und
• – c die Lage der Asymptote angibt, das heißt die Endtemperatur.

In this context, it can be provided that in the determination of the temperature and / or the provision of the overheating protection, a comparison of the time information and the temperature information takes place with a known cooling function. The cooling curve of the sensor body essentially follows an asymptotic e-function T = f (t) = a × e -bt + c, in which

• T denotes the temperature and t denotes the time;
• A represents the distance of the starting point from the asymptote (a + c), that is, the starting temperature;
• B is a measure of the combination of the material properties thermal conductivity and specific heat capacity and the flow velocity of the heat transfer medium, or a measure of the energy removal; and
• - c indicates the position of the asymptote, that is the final temperature.

It but it can also be useful be that in determining the temperature and / or providing of overheating protection a comparison of the time information and the temperature information with known limits. The only iterative possible and thus elaborate determination of the coefficients a, b and c of the cooling function can be bypassed this way. It will increase the temperature during one Heating phase evaluated, whereby the heating phase by duration and introduced Heating energy is defined. The limit function is dependent the permissible temperature increase related to the ambient temperature Equation or table to deposit, where in each case the concrete constructive application case to consider is. A comparison of the determined temperature increase with the corresponding limit value provides the decision as to whether it is a critical condition or not.

The Invention will be exemplified below with reference to the accompanying drawings explained.

It demonstrate:

1 a highly simplified schematic block diagram of a motor vehicle heater;

2 a graph illustrating two typical cooling curves of a sensor body;

3 a flow sensor with four contacts operating according to the calorimetric measuring principle;

4 a flow sensor with three contacts operating according to the calorimetric measuring principle;

5 a flow sensor operating on the calorimetric measuring principle with two contacts;

6 a typical temperature profile of a sensor element for alternating heating and cooling phases.

At the in 1 only motor vehicle heater shown schematically 10 it may in particular be an auxiliary and / or auxiliary heater. The heater 10 has a burner 22 on, through which a heat transfer medium 14 It can be heated by a heat exchanger 24 flows. In this case, the heat exchanger 24 an inflow 26 and a drain 28 on. A control unit 30 is intended to control the entire operation of the heater 10 to control or regulate.

According to the state The technology is usually at least two temperature sensors in such heaters available. Overheating protection, for example in the form of a PTC, a bimetallic switch or a Melting insert, and a temperature-dependent resistor (NTC) to actual temperature determination.

Instead of these two temperature sensors is as shown by 1 a single flow sensor operating on the calorimetric measuring principle 12 provided, which serves both as overheating protection as well as the actual temperature measurement. Although in principle other solutions are possible, stands the flow sensor 12 over only two connection lines 32 with the controller 30 in connection.

Such flow sensors originally served to detect the known material properties, such as thermal conductivity and specific heat capacity, the flow velocity of the medium, or conversely, to close at a known flow rate on the current material properties. The sensor element is for this purpose by means of a heating resistor heated beyond the ambient temperature. The curve curve resulting from the measurements carried out during the subsequent cooling phase is evaluated in order to conclude on the flow velocity or the material properties. The use of a flow sensor in the conventional sense thus requires either the knowledge of the media properties or the media speed. For example, in the case of heating appliances, however, these are not to be taken for granted due to the frost and corrosion protection rates or the different pump capacities and flow resistances, which are metered differently in practice.

Therefore, it is assumed according to the invention that the energy-transporting heat transfer medium 14 must be able to carry away at least the same amount of energy that is introduced by the heater. It is completely irrelevant at what speed the medium 14 flows or how high its heat capacity is. The only thing that is important is the determined curve, which is a measure of the energy balance of the system and which, in addition, depending on the length of the cooling phase, can directly measure the temperature of the medium or allow it to be deduced by extrapolation. As mentioned, the essential difference to the conventional gradient evaluation is that a defined electrical heating of the sensor takes place, which represents a defined energy supply and, as a result, can be deduced by the subsequent cooling to a defined energy removal.

• – a den Abstand des Anfangspunktes von der Asymptote (a+c), das heißt die Ausgangstemperatur darstellt;
• – b ein Maß für die Kombination der Stoffeigenschaften Wärmeleitfähigkeit und spezifische Wärmekapazität und die Strömungsgeschwindigkeit des Wärmeträgermediums ist, beziehungsweise ein Maß für den Energieabtransport; und
• – c die Lage der Asymptote angibt, das heißt die Endtemperatur.

2 shows two typical cooling curves of the sensor body of the flow sensor 12 , where the temperature in ° C over time in seconds is plotted. The two illustrated curves follow an asymptotic e-function, with: T = f (t) = a × e -bt + c, in which

• A represents the distance of the starting point from the asymptote (a + c), that is, the starting temperature;
• B is a measure of the combination of the material properties thermal conductivity and specific heat capacity and the flow velocity of the heat transfer medium, or a measure of the energy removal; and
• - c indicates the position of the asymptote, that is the final temperature.

For the in 2 Curves I and II shown a = 10K, c = 80 ° C and b = 0.5 (curve 1) and b = 1.3 (curve 2). Out 2 It can be seen that the size b as a measure of the energy removal significantly influences the course of the decay curve.

3 shows an embodiment of a flow sensor 12 in which a separately controlled heating element 16 in the form of a heating resistor and a separately controlled temperature measuring device 18 is provided in the form of a temperature-dependent measuring resistor. The heating element 16 and the temperature measuring device 18 are alternately driven and four contacts are required. The term "alternately" means in this and comparable contexts that during certain periods of time a heating takes place and at other time periods a measurement takes place; a measurement in the immediate aftermath of the heating or heating immediately after the measurement are not required.

4 shows an embodiment of a flow sensor 12 in which a heating element 16 in the form of a heating resistor and a temperature measuring device 18 are connected in series in the form of a temperature-dependent measuring resistor, wherein a center tap is provided. The heating element 16 and the temperature measuring device 18 are operated alternately and three contacts are required.

5 shows a particularly preferred embodiment of a flow sensor 12 in which a heating element 16 and a temperature measuring device 18 through a shared component 20 are formed, which consists in the case shown of a suitable resistance element. The resistance element 20 is used alternately as a heating resistor and as a temperature-dependent measuring resistor, so that only two contacts are required.

In the 3 to 5 the measuring voltage is U _M and the heating voltage U _H.

6 shows a typical course of a sensor body temperature (for example, for the temperature sensor 12 according to 5 ) which results when the heating and the

temperature detection done alternately. The temperature in ° C is above the Time in seconds and the measurement phases are labeled M. while the heating phases are denoted by H.

The in the above description, in the drawings and in the claims disclosed features of the invention can both individually and also in any combination for the realization of the invention be essential.

10

heater

10

Car heater

12

flow sensor

14

Heat transfer medium

16

heating element

18

Temperature measuring device

20

component

22

burner

24

heat exchangers

26

inflow

28

outflow

30

control unit

32

connecting cables

Claims (14)

Heater ( 10 ), in particular motor vehicle heating device ( 10 ), the means for determining a temperature and / or acting as overheating protection means, characterized in that the means for determining the temperature and / or acting as overheating protection means a working according to the calorimetric measuring principle flow sensor ( 12 ). Heater ( 10 ) according to claim 1, characterized in that the flow sensor ( 12 ) is arranged so that it at least partially from a heat transfer medium ( 14 ) is surrounded. Heater according to claim 1 or 2, characterized in that the flow sensor ( 12 ) a heating element ( 16 ) and a temperature measuring device ( 18 ) having. Heater according to one of the preceding claims, characterized in that the heating element ( 16 ) and the temperature measuring device ( 18 ) by a component ( 20 ) or a group of components are formed, which or alternately as a heating element ( 16 ) and as a temperature measuring device ( 18 ) is operated. Heater according to claim 3 or 4, characterized in that via the heating element, a defined energy supply can take place and that via a through the temperature measuring device ( 18 ) recorded subsequent cooling can be concluded on an energy removal. Use of a flow sensor operating according to the calorimetric measuring principle ( 12 ) as a temperature sensor. Use of a flow sensor operating according to the calorimetric measuring principle ( 12 ) according to claim 6, characterized in that the flow sensor ( 12 ) has the function of overheating protection. Use of a flow sensor according to the calorimetric measuring principle according to claim 6 or 7, characterized in that the flow sensor ( 12 ) is provided for determining the temperature. Use of a flow sensor operating according to the calorimetric measuring principle according to one of claims 6 to 8, characterized in that the flow sensor ( 12 ) a heating element ( 16 ) and a temperature measuring device ( 18 ) having. Use of a calorimetric measuring principle flow sensor according to claim 9, characterized in that the heating element ( 16 ) and the temperature measuring device ( 18 ) by a component ( 20 ) or a group of components are formed, which or alternately as a heating element ( 16 ) and as a temperature measuring device ( 18 ) is operated. Use of a calorimetric measuring principle flow sensor according to claim 9 or 10, characterized in that via the heating element ( 16 ) a defined energy supply takes place and via a through the temperature measuring device ( 18 ) subsequent subsequent cooling is concluded on a removal of energy. Method for determining a temperature and / or for providing overheating protection in a vehicle heater, characterized in that using a calorimetric measuring principle flow sensor ( 12 ) At least two times a temperature of a heat transfer medium is measured. Method according to claim 12, characterized in that in determining the temperature and / or providing of overheating protection a comparison of the time information and the temperature information with a known cooling function he follows. Method according to claim 12 or 13, characterized in determining the temperature and / or providing of overheating protection a comparison of the time information and the temperature information done with known limits.